That makes reasonable sense. Maybe that will be enough to tickle someone the right way and come up with something more concrete. I will probably try to follow that line of reasoning a bit, too, and see if I come up with anything.

#1 is probably juts a test point or something. I don't think it's an actual component. The second and the third might be optocouplers, but it's very difficult to tell. Those schematics are a mess, I can't read half of it. And they certainly don't use standard symbols.